Link to HTML5 Geolocation PositionOptions docs

I think this change passes everything but the travis build errored out after 45 minutes, reporting:

    2013-09-03 12:30:53,425 check-examples: phantomjs bin/check-example.js build/hosted/HEAD/examples/navigation-controls.html?mode=advanced

    No output has been received in the last 10 minutes, this potentially indicates a stalled build or something wrong with the build itself.